Visualization updates

The first two commits remove jtidy (which has not really been maintained for the last ten years and has never really been designed as a reusable library) and replaces it with the validator.nu html parser. This should also be a useful change if you ever want to replace the xslt logic with  some other mechnism to allow games to generate visualization html.

The following two commits use the new flexibility offered by using a modern html parser to add svg rendering to the visualization logic, see my diplomacy clone https://github.com/fhars/ggp-games for an example.